1. Field of the Invention
The present invention relates to a sheet processing technique to perform a specific process to a sheet.
2. Description of the Related Art
In a sheet processing apparatus for performing a folding process to a bundle of sheets by a pair of folding rollers and a folding blade, a large rotation load is exerted on the pair of folding rollers in a period from when the bundle of sheets as an object of the folding process is pressed into the pair of folding rollers to when the folding process by the pair of folding rollers is completed. Thus, in order to cause the pair of folding rollers to generate a high torque, it is general that the rotation speed of a motor is reduced by a gear train, and the pair of folding rollers are rotated and driven only in the state of the reduced rotation speed (state of low speed rotation and high torque).
However, in the folding process of the bundle of sheets, the very large torque is required only in the period from when the bundle of sheets as the object of the folding process is pressed into the pair of folding rollers to when the folding process by the pair of folding rollers is completed, and the high torque is not necessarily required for the rotation driving of the pair of folding rollers in a period other than that (for example, transport of the bundle of sheets to the downstream side after the folding process).
Thus, in view of throughput, there is a problem when the pair of folding rollers is driven at the low speed rotation in order to provide the high torque even in the mere transport of a bundle of sheets in which the high torque is not required as stated above.